Method and apparatus to provide a GMR lapping plate texturization using a photo-chemical process

ABSTRACT

A system and method are described for manufacturing a lapping plate. In one example, the lapping plate is made by covering a Tin-Antimony plate with photoresist and exposing the resulting photoresist layer with UV light through a wire mesh mask. After development, the non-etch areas can serve as land areas for diamond charging. Such a method may lead to fewer artifacts on the lapping plate and smaller diamond particle dimensions resulting in better processing of read/write heads, especially GMR heads.

FIELD OF THE INVENTION

[0001] The present invention pertains to a method and apparatus forprocessing slider devices for hard disk drives and the like. Moreparticularly, the present invention pertains to lapping slider airbearing surfaces, especially for GMR type heads.

BACKGROUND TO THE INVENTION

[0002] Hard disk drives are common information storage devicesessentially consisting of a series of rotatable disks that are accessedby magnetic reading and writing elements. These data transferringelements, commonly known as transducers, are typically carried by andembedded in a slider body that is held in a close relative position overdiscrete data tracks formed on a disk to permit a read or writeoperation to be carried out. In order to properly position thetransducer with respect to the disk surface, an air bearing surface(ABS) formed on the slider body experiences a fluid air flow thatprovides sufficient lift force to “fly” the slider and transducer abovethe disk data tracks. The high speed rotation of a magnetic diskgenerates a stream of air flow or wind along its surface in a directionsubstantially parallel to the tangential velocity of the disk. The airflow cooperates with the ABS of the slider body which enables the sliderto fly above the spinning disk. In effect, the suspended slider isphysically separated from the disk surface through this self-actuatingair bearing. The ABS of a slider is generally configured on the slidersurface facing the rotating disk, and greatly influences its ability tofly over the disk under various conditions.

[0003] As shown in FIG. 1 an ABS design known for a common catamaranslider 5 may be formed with a pair of parallel rails 2 and 4 that extendalong the outer edges of the slider surface facing the disk. Other ABSconfigurations including three or more additional rails, with varioussurface areas and geometries, have also been developed. The two rails 2and 4 typically run along at least a portion of the slider body lengthfrom the leading edge 6 to the trailing edge 8. The leading edge 6 isdefined as the edge of the slider that the rotating disk passes beforerunning the length of the slider 5 towards a trailing edge 8. As shown,the leading edge 6 may be tapered despite the large undesirabletolerance typically associated with this machining process. Thetransducer or magnetic element 7 is typically mounted at some locationalong the trailing edge 8 of the slider as shown in FIG. 1. The rails 2and 4 form an air bearing surface on which the slider flies, and providethe necessary lift upon contact with the air flow created by thespinning disk. As the disk rotates, the generated wind or air flow runsalong underneath, and in between, the catamaran slider rails 2 and 4. Asthe air flow passes beneath the rails 2 and 4, the air pressure betweenthe rails and the disk increases thereby providing positivepressurization and lift. Catamaran sliders generally create a sufficientamount of lift, or positive load force, to cause the slider to fly atappropriate heights above the rotating disk. In the absence of the rails2 and 4, the large surface area of the slider body 5 would produce anexcessively large air bearing surface area. In general, as the airbearing surface area increases, the amount of lift created is alsoincreased.

[0004] As-illustrated in FIG. 2, a head gimbal assembly 40 oftenprovides the slider with multiple degrees of freedom such as verticalspacing, or pitch angle and roll angle which describe the flying heightof the slider. As shown in FIG. 2, a suspension 74 holds the HGA 40 overthe moving disk 76 (having edge 70) and moving in the directionindicated by arrow 80. In operation of the disk drive shown in FIG. 2,an actuator 72 moves the HGA over various diameters of the disk 76(e.g., inner diameter (ID), middle diameter (MD) and outer diameter(OD)) over arc 78.

[0005] Giant Magnetoresistive (GMR) heads are being used more and morefor advanced hard disk drive (e.g., capable of storing more than 80gigabytes of data). GMR heads, which are well-known in the art, includecomponents generally located in the middle of the trailing portion ofthe slider (not the air bearing surface of the slider). These componentsare quite susceptible to damage induced by head manufacturing processes,particularly during lapping processes. An example of a lapping operationand a plate used for the operation are shown in U.S. Pat. No. 4,866,886to Holmstrand. The plate includes an embedded abrasive (e.g., diamondparticles) and is spun so as to abrade a surface of the GMR head held inplace over the moving plate. An abrasive slurry can be added to theplate to facilitate the abrading process. As known in the art, thelapping plates include “lands” and “grooves.” The lands are at a greaterheight than the grooves on the lapping plate and come into contact withthe slider surface. The grooves become a repository for the abrasiveparticles (e.g., the particles in the slurry, the particles originallyembedded in the lapping plate, etc.). The grooves also become arepository for the material removed from the slider.

[0006] Using lapping plates as described above can cause problems in themanufacture of GMR heads. The relatively large abrasive particles candamage the GMR head portion of the slider. One approach to improvinghead manufacture is to use smaller particles in the lapping plate. Asthe abrasive particles become smaller, however, it becomes harder tocontrol lapping plate flatness, texture, roughness and cleanliness tosuccessfully embed diamond abrasive, for example (sometimes referred toas the charging process).

[0007] The texturing process for the lapping plate could have a profoundimpact on GMR head performance of the slider. The texture of the lappingplate will have an effect on slider properties such as surface finish,pole tip recession (or PTR), smearing (i.e., potentially causing deviceshorting), and bulk removal rates.

[0008] The Holmstrand reference refers to one such texturing process. InHolmstrand, small cavities in the surface of the lapping plate arecreated using a glass bead blasting apparatus. Using the texturingprocess of Holmstrand, the PTR can be controlled to an order of 28microns. With current sliders, however, the PTR is controlled to lessthan 0.01 microns. One possible reason for such a high value may be thatthe cavities serve as reservoirs for abrasive sludge instead of allowingthe sludge to leave the surface of the disk (e.g., through centrifugalforce of, the spinning lapping plate). Accordingly, this texturingprocess is not acceptable for current slider manufacturing.

[0009] Another process is where spiral grooves are provided in thesurface of the lapping plate. The spiral grooves are formed using afacing machine. The width and spacing of the lands and grooves isreferred to as the “pitch” of the lapping plate. After the spiralgrooves are formed, the lapping plate is further processed by“deburring” (or shaving), which knocks off high peaks and leaves thelands for diamond charging. One problem with the deburring process isthat it typically induces machine related burrs, uneven land to grooveratios, broken edges of the plateau and varying depths of the groove4.These, in turn, could directly or indirectly affect the properties ofthe finished slider. One solution is to finely control the operation andfunction of the facing machine, though doing so can be an expensive andtime-consuming process.

[0010] Yet another process for fabricating a lapping plate includes theuse of a diamond-textured ring process. As described in U.S. Pat. No.4,037,367 to Kruse, the natural flow of grooves facilitates a relativeeasy removal of sludge unlike that shown in the Holmstrand patent.Though the process in Kruse may improve bulk removal rates and pole tiprecession, the roughness of the land area is uneven and excessive platematerial debris may be caught in the grooves and be difficult to remove.In such a case it may become harder to charge the land areas withsmaller size diamond particles (i.e., ones have a mean diameter of, 1.0microns). Another disadvantage of this process is that the amount ofplate debris increases with increased softness of the plate material,thus limiting this process to hard plate materials.

[0011] In view of the above, there is a need for an improved lappingplate and method of manufacturing such plates the reduces plate debris.

SUMMARY OF THE INVENTION

[0012] According to an embodiment of the present invention, a method andapparatus for manufacturing a lapping plate are provided. In oneembodiment, the metal plate is first chemically etched using mask-etchprocedure that are known in the silicon chip manufacturing field. Theareas of the metal plate that are not etched during this procedure formlands in which diamond charging can be accomplished. The resultinglapping plate may be used with sensitive GMR heads because of therelatively small diamond particles that can be charged into the metalplate and their relatively even distribution across the plate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a perspective view of a flying slider with a read andwrite element assembly having a tapered conventional catamaran airbearing slider configuration.

[0014]FIG. 2 is a plan view of a mounted air bearing slider over amoving magnetic storage medium.

[0015]FIG. 3 is a flow diagram of a method of fabricating a lappingplate according to an embodiment of the present invention.

[0016]FIGS. 4a-l are views of a lapping plate and an apparatus forimplementing the method of FIG. 3 for fabricating lapping plateaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

[0017] Referring to FIG. 3, a flow diagram is shown of a methodaccording to an embodiment of the present invention. In this embodiment,the lapping plate is made of an alloy of Tin and Antimony. In block 301,the lapping plate is machined to make it flat.(e.g., less than 2 micronsof roughness). In block 303, the lapping plate may then be polished ortextured (depending on the quality of the machining process). Forexample a burr-free polishing cloth may be used with a very-fineabrasive to remove any artifacts remaining from the machining operationof block 301. In block 305, the lapping plate is then heated in an oven(for example, at 60° C. for approximately 15 minutes). The heated plateis then laminated with a photoresist (e.g., the FL13 photoresistmanufactured by Shipley Company, LLC, Marlborough, Mass.) at a thicknessof 30 μm. The remnant heat in the lapping plate assists in facilitatingan even flow of the photoresist over the surface of the plate. Inaddition, the laminator device that is used to put the photoresist ontothe lapping plate can heat the photoresist while pressing it onto theplate to prevent air bubbles between the plate and photoresist.

[0018] In block 309, the photoresist layer is selectively exposed (e.g.,to electromagnetic radiation such as ultra violet light) for apredetermined amount of time (e.g., 8-10 seconds). In this embodiment, astainless steel mesh fabric, such as a MicroMesh product by MicroMetallic, Ltd. (Mersyside, UK), is used have a selected hole dimensionand spacing. Other types of masks may be used including those used instandard photolithographic processes. Using a the stainless steel meshfabric may make the expose operation quicker and/or more inexpensivecompared to standard photolithographic masking. In block 311, thelapping plate and exposed photoresist are developed. In one embodiment,the photoresist is developed by rotating the plate at a predeterminedspeed and spraying developer solution onto the photoresist layer vianozzles for a predetermined amount of time (e.g., enough time to allowsufficient dissolving of selected areas of the photoresist layer). Inblock 313, the lapping plate is washed with deionized (DI) water toremove the developer solution and the dissolved photoresist. The lappingplate is then dried (e.g., clean air supplied via a nozzle over thesurface of the plate).

[0019] In block 315, the lapping plate is etched. In this embodiment ofa Tin-Antimony alloy plate, a 1:3 ratio of hydrochloric acid to nitricacid may be used as the etchant. Such acids may be diluted withdeionized water depending on the depth of etching into the plate that isdesired. Thus, in block 315, the plate is wet-etched for a predeterminedamount of time (e.g., five minutes). In this embodiment, the lappingplate is submerged in an etchant bath and the etchant is continuouslyagitated so that the etching depth is kept uniform over the area of theplate. After the etching operations, the plate can then be rinsed indeionized water and air dried in a manner similar to that above. Inblock 317, the remaining photoresist is removed from the lapping plate(e.g., using an acetone solution to dissolve the undevelopedphotoresist). In block 319, the lapping plate is cleaned by rinsing itin deionized water and air drying it in a manner similar to that above.Alternatively, the rinsed lapping plate may be dried with an appropriatecloth.

[0020] In block 321, the lapping plate is charged with diamondparticles. As stated above, it is advantageous for the lapping of GMRheads if the diamond particles are relatively small in diameter. Thoughdiamonds having a mean diameter of 100 nm to 125 nm may be used, in thisexample, the charging apparatus deposits diamonds having a mean diameterof less than 50 nanometers. The diamonds are deposited into the landareas of the lapping plate (i.e., the areas of the lapping plate thathave not been etched in the processes above). The resulting plate mayhave a very uniform placement of small diameter diamond particles. Usinga lapping plate constructed according to an embodiment of the presentinvention, a pole tip recession for the read/write head may be very low(e.g., between 2 and 3 nanometers) resulting in improved performance forthe head in the disk drive environment.

[0021] Referring to FIGS. 4a-1 a lapping plate and apparatus forfabricating one are shown according to an embodiment of the presentinvention. In FIG. 4a, a metal disk 410 made of an alloy of Tin andAntimony is provided. In this example, the disk has a thickness of 2.5inches and a diameter of 16 inches. In FIG. 4b, the disk 410 is placedon a spindle motor 412 and made flat by machining apparatus 414. In FIG.4c, the disk 410 is polished with a burr-free polishing cloth (e.g.,with machine 416). The disk can then be laminated with. photoresist. InFIG. 4d, the metal disk 410 is spun by spindle motor 412 afterphotoresist is deposited by deposition apparatus 418.

[0022] Once the photoresist layer 426 is set to the metal disk, a mask,such as a wire mesh 424, can be placed over the photoresist layer (SeeFIG. 4e). In this example, a UV radiation source 422 exposes portions ofthe photoresist layer 426 through the wire mesh 424. The metal disk 410may be placed on a support 420 during this exposure operation. In FIG.4f, developer is disposed onto the metal disk via apparatus 428. Asknown in the art, developer reacts with the exposed or unexposed areasof the photoresist depending on the type of photoresist being used. InFIG. 4g, the undesired photoresist is removed, for example, by sprayingthe metal disk with deionized water.

[0023] The metal disk 410 with developed photoresist layer 426 isetched. As seen in FIG. 4h, the metal disk 410 can be lowered intoetchant 436 in tub 438 while resting on holder 434. An agitator may beprovided to vibrate the tub 438 so as to improve the etching process. InFIG. 4i, the photoresist layer 426 is removed with apparatus 440. InFIG. 4j, the metal disk 410 is cleaned with an appropriate cloth 442. InFIG. 4k, the metal disk 410 is diamond charged with apparatus 444 todispose diamond particles of a selected size into the unetched landareas of the metal disk to finish the lapping plate. Once completed, thelapping plate may be used to lap sliders including GMR sliders held byapparatus 446 (e.g., see FIG. 4l).

[0024] While the present invention has been described with reference tothe aforementioned applications, this description of the preferredembodiments is not meant to be construed in a limiting sense. It shallbe understood that all aspects of the present invention are not limitedto the specific depictions, configurations or dimensions set forthherein which depend upon a variety of principles and variables. Variousmodifications in form and detail of the disclosed apparatus, as well asother variations of the present invention, will be apparent to a personskilled in the art upon reference to the present disclosure. It istherefore contemplated that the appended claims shall cover any suchmodifications or variations of the described embodiments as fallingwithin the true spirit and scope of the present invention.

[0025] For example, though in FIGS. 3 and 4, a wire mesh is used as amask, the location and dimensions of the land areas for diamond chargingmay be more accurately controlled by using a more conventional mask asknown in the art.

What is claimed is:
 1. A method of manufacturing a lapping platecomprising: selectively etching a metal plate; and imbedding diamondparticles into said metal plate.
 2. The method of claim 1 wherein saidetching step includes: applying a photoresist layer to said metal plate;and selectively removing photoresist from a surface of said metal plate.3. A method of manufacturing a lapping plate comprising: applying aphotoresist layer to a metal plate; selectively exposing areas of saidphotoresist layer to electromagnetic radiation; developing saidphotoresist layer; etching areas of said metal disk; and imbeddingdiamond particles into non-etched areas of said metal disk.
 4. Themethod of claim 3 wherein said selectively exposing operating includes:providing a mask between an electromagnetic radiation source and saidphotoresist layer;
 5. The method of claim 4 wherein said mask is a wiremesh.
 6. The method of claim 4 wherein said electromagnetic radiation isultra-violet radiation.
 7. The method of claim 4 wherein saidphotoresist is a positive photoresist.
 8. The method of claim 4 whereinsaid photoresist is a negative photoresist.
 9. The method of claim 4wherein said etching operation is a wet-etch operation.
 10. The methodof claim 4 wherein said diamond particles have a diameter less than 50nanometers.
 11. A method of fabricating a read/write head for a diskdrive, comprising: applying a photoresist layer to a metal plate;selectively exposing areas of said photoresist layer to electromagneticradiation; developing said photoresist layer; etching areas of saidmetal disk; imbedding diamond particles into non-etched areas of saidmetal disk to create a lapping plate; and lapping a read/write head withsaid lapping plate.
 12. The method of claim 11 wherein said selectivelyexposing operating includes: providing a mask between an electromagneticradiation source and said photoresist layer;
 13. The method of claim 12wherein said mask is a wire mesh.
 14. The method of claim 12 whereinsaid electromagnetic radiation is ultra-violet radiation.
 15. The methodof claim 12 wherein said photoresist is a positive photoresist.
 16. Themethod of claim 12 wherein said photoresist is a negative photoresist.17. The method of claim 12 wherein said etching operation is a wet-etchoperation.
 18. The method of claim 12 wherein said diamond particleshave a diameter less than 50 nanometers.
 19. The method of claim 18wherein said read/write head is a GMR read/write head.
 20. The method ofclaim 18 wherein a pole tip recession for said GMR read/write head isbetween 2 and 3 nanometers.
 21. A lapping plate comprising: a metalplate including a plurality of etched areas, said etched areas formedfrom an etching operation through a developed photoresist mask; anddiamond particles imbedded into non-etched areas of the metal plate. 22.The lapping plate of claim 21 wherein said photoresist is a positivephotoresist.
 23. The lapping plate of claim 21 wherein said photoresistis a negative photoresist.
 24. The lapping plate of claim 21 whereinsaid metal plate is wet-etched.
 25. The lapping plate of claim 21wherein said diamond particles have a diameter less than 50 nanometers.